Today, both chemical and energy industries rely on petroleum as the principal source of carbon and energy. Methane is underutilized as a chemical feedstock, despite being the primary constituent of natural gas, an abundant carbon resource. Factors limiting its use include the remote locations of known reserves, its relatively high transportation costs and its thermodynamic and kinetic stability. Methane's main industrial use is the production of synthesis gas or syngas via steam reforming at high temperatures and pressures. Syngas in turn can be converted to methanol also at elevated temperatures and pressures. The production of methanol is important because methanol can be used to produce important chemicals such as olefins. The above two step process for the production of methanol is expensive and energy intensive with corresponding environmental impacts.
Selective oxidation of methane has been studied for over 30 years by individual, academic and government researchers with no commercial success. The key challenges to a commercial direct methane oxidation process are the inertness of methane relative to intermediates and oxygenate products and designing a catalytic process for direct gas phase reaction with high conversion and selectivity. For example, Sen et al. in New J. Chem, 1989, 13, 755-760 disclose the use of Pd (O2C Me)2 in trifluoroacetic acid for the oxidation of methane to CF3CO2Me. The reaction is carried out for 4 days at a pressure of 5516-6895 kPa (800-1000 psi). E. D. Park et al. in Catalysis Communications, Vol. 2 (2001), 187-190, disclose a Pd/C plus Cu (CH3COO)2 catalyst system for the selective oxidation of methane using H2/O2. L. C. Kao et al. in J. Am. Chem. Soc., 113 (1991), 700-701 disclose the use of palladium compounds such as Pd (O2CC2H5)2 to oxidize methane to methanol in the presence of H2O2 and using trifluoroacetic acid as the solvent. U.S. Pat. No. 5,585,515 discloses the use of catalysts such as Cu(I) ions in trifluoroacetic acid to oxidize methane to methanol.
Applicants have developed a process which efficiently produces a methanol stream from methane. Generally, the process comprises reacting methane and an oxidant in the presence of a catalyst at oxidation conditions. The resultant product mixture is next processed to give a purified methanol stream and recycle methane and solvent streams.